Browsing by Subject "Radiometers"

Now showing 1 - 2 of 2

Open Access
Millimeter-wave scale metamaterials
(IEEE, 2009-11) Alıcı, Kamil Boratay; Özbay, Ekmel
We review two metamaterial configurations, which are operating at the millimeter-wave scale, in terms of design, fabrication, and characterization. We observed both numerically and experimentally at around 100 GHz a narrow frequency band for which the metamaterial was low loss and had a negative index of refraction. We investigated flat and wedge shaped samples to support our characterization results. We analyzed the transmission band with respect to number of layers at the propagation direction and commented on the bulk nature of these metamaterials. Oblique response of the planar sample was also included in this study. Finally, we demonstrate a device, which yields a rather small angular width at the far field radiation pattern, and composed of a horn antenna and flat metamaterial slabs at the propagation direction. ©2009 IEEE.
Open Access
RF radiometery sensor sensitivity and detection profile
(IEEE, 2008-11) El-Sharkawy, A.-M.M.; Sotiriadis, P. P.; Bottomley, P. A.; Atalar, Ergin
Temperature sensing using microwave radiometry has proven value for non-invasively measuring the absolute temperature of tissues inside the human body. However, current clinical radiometers operate in GHz or infrared frequency ranges; this limits their depth of penetration since the human body is not "transparent" at these frequencies. To address this problem, we have previously designed and built an advanced, near-field radiometer operating at VHF frequencies (64MHz) with a ∼100 KHz bandwidth. The radiometer has performed accurate temperature measurements to within ±0.1°C, over a tested physiological range of 28-40°C in saline phantoms whose electric properties match those of human tissue. In this work we analyze radiofrequency (RF) coil designs suitable for RF Radiometry. We investigate the coil profile sensitivity to look where temperature information is coming from and the depth of penetration associated with the receiver used. We also look into the virtues of using multi-turn coils versus single loop coils. We conclude that by using multi-turn coils the received noise signal is more sensitive to sample noise and temperature can be estimated more accurately especially with the use of smaller receivers. © 2008 IEEE.